Going in on a building or apartment with a group of friends, your in-laws, or even complete strangers isn’t as crazy as it sounds.

The average price for a Manhattan apartment just hit $1.7 million; Brooklyn’s numbers, though not yet in the seven figures, are nearly as forbidding. Which means that owning a home in the city that isn’t a sixth-floor railroad apartment is becoming more and more of a pipe dream. For the brave ones, however, there is another option: joining forces with those outside your immediate nuclear family and buying something together. And no, you don’t have to be a member of a ’70s-era psychotherapy cult. Otherwise-normal New Yorkers are pooling their resources to buy brownstones with backyards, summer houses upstate, and even just plain old two-bedroom apartments they otherwise couldn’t afford. The upsides are plenty (more bang for your buck, shared child care, a sense of community). But there are trade-offs, too: Mixing friendship, real estate, and money is as slippery as it gets. Here, profiles of five co-home-buyers who went for it, one group that ultimately split up, and why you should always have a prenup.

Friends With Kids Mike Beck and Iris Ng and their son share a townhouse in Prospect-Lefferts Gardens with Sarah and Oliver Gray and their two sons.

Illustration by Murphy Lippincott

Did you plan all along to purchase with friends? Iris: Sarah and I had talked about it as a joke at first. But when my husband, Mike, and I started house-hunting, it quickly became apparent that we couldn’t afford more than a condo, and we had our hearts set on a place with a yard. That’s when Sarah and I started talking seriously. Financially, she and Oliver were very similar to us.

What were the pre-buying discussions like?Oliver: We drew up a document, a kind of agreement between the two couples about the schedule and the renovations. It wasn’t anything that we ran by a lawyer, but it helped us plan. Sarah: We realized the houses in Lefferts Gardens were perfect for what we wanted: a top unit and a bottom unit. We kept our basement communal and accessible to both apartments.

The disadvantages to this setup? Iris: Silly things, I guess. Fixing things like plumbing or snow shoveling, maybe. Like, if you have to nag one husband, in our case you have to nag two.

And the upsides?Mike: We had children at the same time, and not only did we build an extended family, but there’s also the benefit of built-in child care. When you look back at how many times one couple handed the monitor off to another couple, it’s pretty amazing. We saved so much on babysitters.

But Sarah and Oli are about to move back to England? Mike: We knew it would happen eventually, that one party would move on. We thought we’d put the house on the marketóbut then decided to buy Sarah and Oli out.Iris: It’s super-sad. I’ll really miss raising the kids together. Mike: The real pain point is the kids. They’re like brothers. Iris: But Sarah and Oli and Mike and I have already talked about doing it again when we retire.